81139545 has 12 divisors (see below), whose sum is σ = 140641956. Its totient is φ = 43274400.

The previous prime is 81139523. The next prime is 81139549. The reversal of 81139545 is 54593118.

81139545 is a `hidden beast` number, since 81 + 1 + 39 + 545 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 8139609 + 72999936 = 2853^2 + 8544^2 .

It is not a de Polignac number, because 81139545 - 2⁹ = 81139033 is a prime.

It is a super-3 number, since 3×81139545³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81139549) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 901506 + ... + 901595.

It is an arithmetic number, because the mean of its divisors is an integer number (11720163).

Almost surely, 2^81139545 is an apocalyptic number.

It is an amenable number.

81139545 is a deficient number, since it is larger than the sum of its proper divisors (59502411).

81139545 is a wasteful number, since it uses less digits than its factorization.

81139545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1803112 (or 1803109 counting only the distinct ones).

The product of its digits is 21600, while the sum is 36.

The square root of 81139545 is about 9007.7491639144. The cubic root of 81139545 is about 432.9231960948.

The spelling of 81139545 in words is "eighty-one million, one hundred thirty-nine thousand, five hundred forty-five".